This invention relates to dynamoelectric machines with a radial path air-cooled rotor and particularly to means for improving coolant flow therethrough.
The subject matter of commonly assigned Application Ser. No. 552,592, filed Nov. 16, 1983 by Pavlik et al., now U.S. Pat. No. 4,508,885 and Ser. No. 607,853, filed of even date herewith by Hammer et al., is incorporated herein by reference.
In the earlier copending application are described the general characteristics of machines with radial path air-cooled rotors as they have been made heretofore and an improvement thereto for providing better flow into the slot channels by means of a channel inlet fairing. This provides better cooling of the rotor so that machine size and noise can be reduced. The present invention has to do with machines of the same general character but with another aspect for improving coolant flow and reducing machine size and noise.
In addition, the above-mentioned second copending application relates to other features for similar purposes. It is advantageous to employ the features of the above-mentioned applications, either individually or together, with those of the present invention. However, any of such features may be individually used to improve the cooling of machines.
In machines with radial air cooling of the rotor in accordance with the prior art, the air is supplied to the end turn region through a stationary inlet duct that extends substantially radially from the periphery of the machine. The air then flows radially inward from the inlet duct, entering the interior to the retaining ring and field winding end turns and flowing in the axial direction with little or no tangential velocity component. Part of the air flows radially outward, cooling the end turns and exits the retaining ring through ventilation holes. The remaining air passes into the field winding slot channels and hence radially outward through a number of slits in the field winding, cooling the body portion of the winding. The air then exits through radial holes in the rotor wedges and enters the air gap. The air from the body portion of the winding flows axially and circumferentially along the air gap and joins the air from the end turn portion of the winding. This combined exhaust flow then is dumped interior to the machine enclosure and exits through the cooler where heat is removed. The air then continues to recirculate.
In such a configuration, the rotor itself is the blower which must produce the required pressure-volume characteristics to obtain the desired flow. If the rotor is unable to meet the requirements, present practice dictates that rotor mounted blowers be employed which have the adverse effects of increasing machine weight and size, airborne noise levels and power consumption.
The present invention provides a means to decrease the inlet pressure loss for the coolant gas entering the field winding subslots and end turns by an amount approximately equal to the available driving differential static pressure produced by the rotor.
The flow path is improved by modifying the inlet duct configuration to include means for rotationally directing coolant out of said duct in the direction of rotation of the rotor. This means comprises, for example, a plurality of inlet guide vanes in fixed locations between axially inner and outer walls of the inlet duct. The guide vanes are each a member extending substantially the entire distance between the walls of the duct proximate the end of the inlet duct adjacent the end turns. They are on an angle relative to a direct radius from the shaft axis so that their radial lower edge is circumferentially spaced from their upper edge in the direction of rotor rotation. Preferably, each of the inlet guide vanes has an airfoil configuration with smoothly curved major surfaces between their upper and lower edges and those edges are smoothly rounded. The vanes may take other forms so long as they impart a tangential velocity to the coolant as it leaves the inlet duct. The invention is also useful in combination with the features addressed by one or both of the above-mentioned copending applications although it may also be independently used.